Final answer:
Hematopoiesis takes place in different sites depending on the age of the individual. Prior to birth, it occurs in the yolk sac, fetal liver, spleen, lymphatic tissue, and eventually the red bone marrow. After birth, it mainly occurs in the red marrow of spongy bone tissue.
Step-by-step explanation:
Hematopoiesis, the process in which blood cells are produced, occurs in various sites depending on the age of the individual. Prior to birth, hematopoiesis occurs in the yolk sac, fetal liver, spleen, lymphatic tissue, and eventually the red bone marrow. After birth, most hematopoiesis occurs in the red marrow, a connective tissue within the spaces of spongy bone tissue. In children, hematopoiesis can also occur in the medullary cavity of long bones, while in adults, it is largely restricted to cranial and pelvic bones, vertebrae, sternum, and the proximal epiphyses of the femur and humerus.